1. Field of the Invention
The present invention relates to a liquid discharging head and apparatus used in a printer, serving as an output terminal of a copier, a facsimile apparatus, a word processor, a host computer or the like, a video printer or the like. More particularly, the invention relates to a liquid discharging head and apparatus having a substrate on which electrothermal transducers (heating elements) for generating thermal energy utilized as energy for recording are formed. That is, the invention relates to a liquid discharging head used in a liquid discharging apparatus for performing recording by discharging a recording liquid (ink or the like) from discharging ports (orifices) as flying droplets to cause the liquid to adhere to a recording medium.
The invention also relates to a cleaning member for removing a substance adhered to the surface of discharging ports of a liquid discharging head for performing recording or the like by discharging ink, and a liquid discharging apparatus including the cleaning member.
2. Description of the Related Art
Liquid discharging apparatuses, particularly ink-jet recording apparatuses, are eagerly required as non-impact recording apparatuses in current business offices and other business processing spots where noise causes problems, and are also being developed and improved in order to realize high-density and high-speed recording, relatively easy maintenance or free of maintenance.
For example, the realization of an ink-jet recording apparatus disclosed in Japanese Patent Application Laid-Open (Kokai) No. 54-59936 (1979) is eagerly desired, because high-density and high-speed recording can be sufficiently expected from its structural features, and the design and the manufacture of a so-called full-line liquid discharging head are very easy.
According to an ink-jet method, for example, color recording can be easily achieved, and a compact recording apparatus can be realized because a liquid discharging head can be manufactured by utilizing a semiconductor technology.
A liquid discharging head including a plurality of ink discharging ports, each having a very small diameter, is used in the ink-jet method. When performing recording, ink is discharged from each of the ink discharging ports in accordance with input of a predetermined recording signal, and the discharged ink adheres onto a recording medium.
A recording apparatus using such a liquid discharging head has the following problems. That is, in the case of an ink-jet recording apparatus for discharging pulverized ink from discharging ports, each having a small diameter, dust present within the apparatus, paper powder from a recording medium, ink droplets and the like sometimes adhere or fixed to the surfaces or surrounding portions of discharging ports 11 shown in FIG. 7. The adhering substance may destabilize the projectile of ink particles discharged from a discharging port, or block the ink discharging port after being dried and solidified, resulting in incapability of ink discharge.
In order to solve such problems, a blade cleaning method has been known in which the adhering substance is wiped by rubbing the outer surface (sometimes described as a face surface) of a member where discharging ports are provided, using a blade (sometimes described as a cleaning member) comprising an elastic member made of polyether urethane rubber, polyester urethane rubber, hydronitrile rubber, silicone rubber or the like.
Recently, in the field of ink-jet recording, high-speed recording is being researched and developed. In a high-speed ink-jet recording apparatus, since the amount of ink discharged per unit time increases, ink tends to adhere to the discharging surface of the liquid discharging head. In order to prevent problems caused by such adherence, it is necessary to frequently perform cleaning of the liquid discharging head by shortening an interval between cleaning operations. Accordingly, the cleaning operation by the cleaning blade is repeated a very large number of times. Hence, improvement in the durability of the cleaning blade is desired.
Furthermore, since the surface of discharging ports of the liquid discharging head is rubbed by the blade a large number of times, improvement in the durability of the surface of the discharging ports is desired.
Conventionally, silicone rubber, hydronitrile rubber, polyester urethane rubber, polyether urethane rubber or the like is used for the elastic member for the cleaning blade used in the blade cleaning method. However, these materials have the following problems.
Silicone rubber has an inferior wear resisting property, and is therefore worn by continuous friction with the liquid discharging head and an ink absorbing member. As a result, cleaning utilizing an edge portion of the blade is sometimes not sufficiently performed. That is, in a worn cleaning blade, ink tends to leak from a contact portion with the surface of the discharging ports of the head, and the adhering substance cannot sometimes be sufficiently removed.
Hydronitrile rubber has an inferior wear resisting property as silicone rubber. A cleaning blade made of hydronitrile rubber is remarkably worn after being used for a long time, due to friction with the liquid discharging head and the ink absorbing member as described above. As a result, ink cleaning is insufficiently performed, and ink and an adhering substance remain in the vicinity of the nozzles, thereby causing inferior accuracy in ink discharge, and a failure in the recorded image, such as deviation between colors.
Urethane rubber does not require addition of an inorganic filler and an oil component, and therefore does not have the problems of damage of the surface of discharging ports of the liquid discharging head due to the filler and harmful effects of the oil component. Since urethane rubber also has a relatively good wear resisting property, it is frequently used as the material for the cleaning blade for the liquid discharging head.
However, although urethane rubber has an excellent wear resisting property, it tends to be subjected to hydrolysis from its structure. Accordingly, due to moisture in the air, or in the case of a liquid discharging apparatus using water ink, urethane rubber is degraded due to water to loose elasticity. As a result, normal contact pressure is not applied to the edge of the blade, and therefore the blade cannot be used for a long time.
Furthermore, since urethane rubber has polar groups in its structure, it tends to absorb water ink which is usually used in an ink-jet recording apparatus, and is therefore swollen by the ink while contacting the ink for a long time. As a result, during a cleaning operation, the cleaning blade extracts ink within nozzles by the affinity, and the ink remains in surrounding portions of the nozzles of respective discharging ports. The remaining ink influences the ink discharging direction, thereby causing oblique ink discharge which degrades accuracy in ink discharge. It is difficult to remove ink remaining on the surface of the blade after cleaning, and the remaining ink sometimes causes a decrease in the cleaning performance at the next cleaning operation.
It is an object of the present invention to solve the above-described problems.
According to one aspect, the present invention which achieves the above-described object relates to a liquid discharging head including a pair of substrates connected in a laminated state, a plurality of liquid channels formed on a connected surface of one of the pair of substrates, a plurality of driving elements, each formed at a predetermined position above a corresponding one of the plurality of liquid channels, and orifices, each communicating with a distal end of a corresponding one of the plurality of liquid channels. A liquid is discharged from each of the orifices by an operation of a corresponding one of the plurality of driving elements. A face surface, serving as an outer surface of a member including the orifices is coated with a material having an ultrahigh water repellent property.
It is preferable that each of the plurality of driving elements is a heating element for generating thermal energy, and that the liquid within each of the plurality of liquid channels is boiled by a corresponding one of the heating elements to generate a bubble in the liquid, and the liquid is discharged from a corresponding one of the orifices due to pressure generated during the generation of the bubble.
According to another aspect, the present invention which achieves the above-described object relates to a liquid discharging head including discharging ports for discharging a liquid, liquid channels communicating with corresponding ones of the discharging ports, heating elements, each formed at a predetermined position above a corresponding one of the liquid channels, and a supply port for supplying the liquid channels with the liquid. The liquid within each of the liquid channels is boiled by a corresponding one of the heating elements to generate a bubble, and the liquid is discharged from a corresponding one of the discharging ports due to a pressure generated during the generation of the bubble. A face surface, serving as an outer surface of a member for forming the discharging ports, is coated with a material having an ultrahigh water-repellent property.
A contact angle made by the material having the ultrahigh water repellent property and the liquid may be at least 150 degrees.
The material having the ultrahigh water-repellent property may include fluoroalkylmethoxysilane.
In the present invention, a liquid discharging apparatus including the above-described liquid discharging head is provided.
In the present invention, a liquid discharging apparatus including the above-described liquid discharging head, and a cleaning member for removing contamination adhering to the face surface, serving as the outer surface of the member where the discharging ports are formed is provided.
It is preferable that the cleaning member includes a polyurethane-rubber elastic member, and a water-repellent film is formed on a surface of the cleaning member contacting the face surface.
According to still another aspect, the present invention which achieves the above-described object relates to a method for manufacturing a liquid discharging head. The method includes the steps of forming a plurality of driving elements on a surface of at least one of a pair of substrates, forming a plurality of liquid channels so as to correspond to the plurality of driving elements, connecting the pair of substrates so as to provide a laminated state in which a surface where the plurality of liquid channels are formed is a connecting surface, forming a member for forming orifices at a distal end of the connected substrate, coating a face surface, serving as an outer surface of the member, with a material having an ultrahigh water-repellent property, and causing the orifices to communicate with corresponding ones of the liquid channels.
According to yet another aspect, the present invention which achieves the above-described object relates to a method for manufacturing a liquid discharging head. The method includes the steps of forming an element substrate made of silicon on a surface of at least one of a pair of substrates, forming a plurality of heating elements for generating thermal energy on the element substrate, forming a plurality of liquid channels corresponding to the plurality of heating elements, connecting the pair of substrates so as to provide a laminated state in which a surface where the plurality of liquid channels are formed is a connecting surface, forming a member for forming orifices at a distal end of a connected substrate; coating a face surface, serving as an outer surface of the member, with a material having an ultrahigh water-repellent property, and causing the orifices to communicate with corresponding ones of the liquid channels.
According to yet a further aspect, the present invention which achieves the above-described object relates to a method for manufacturing a liquid discharging head. The method includes the steps of forming heating elements for generating thermal energy on an element substrate made of silicon, forming liquid channels corresponding to the heating elements, forming a supply port for supplying the liquid channels with a liquid, forming a member where discharging ports for discharging the liquid are formed, coating the member with a material having an ultrahigh water-repellent property, and forming the discharging ports in the coated member.
The coating may be performed according to a film forming method using a chemical vapor reaction or a radical polymerization reaction.
Heat treatment at 150xc2x0 C. may be performed after the coating process.
As for the material having the ultrahigh water repellent property of the present invention, a contact angle of the liquid with respect to the material may be at least 250 degrees, more preferably, at least 155 degrees. The contact angle is measured by a contact-angle meter CA-X150 made by Kyowa Kaimen Kagaku Kabushiki Kaisha.
In the present invention, since the face surface is coated with the material having the ultrahigh water-repellent property, the liquid which may cause contamination is repelled to prevent the liquid from adhering to the face surface. Accordingly, the blockage of the orifices or the discharging ports by particles generated by solidified contamination is prevented, and therefore the liquid discharging head according to the present invention maintains excellent performance for a long time.
Since the surface energy of the surface having the ultrahigh water repellent property is low, ink which tends to be fixed after evaporation hardly adheres to the surface. Even if ink adheres to the surface, its bonding strength is low.
Particularly, in accordance with the spread of use of ink-jet recording apparatuses, a large variety of recording liquids (ink) have been adopted to be used for the apparatuses. Most of these ink liquids include low-solubility materials or materials having end groups which may cause fixing and polymerization. When such ink adheres to the face surface of orifices, these materials are sometimes deposited and solidified, thereby blocking the orifices and degrading the characteristics of the liquid discharging head.
In order to remove contamination, such as ink and the like, adhering to the face surface, a recovering operation is performed by pressing a recovery blade against the face surface during cleaning. As a result, the face surface is sometimes damaged, thereby reducing the water-repellent property or causing dust and the like produced from the scraped face surface to enter the discharging ports, to cause degradation in the quality of printing due to a failure in ink discharge, twisting of the recording material, and the like.
In the present invention, by making the face surface to have an ultrahigh water-repellent property, the surface energy is reduced and therefore the liquid is repelled from the face surface, thereby preventing contamination from adhering to the face surface. Even if contamination adheres to the face surface, it is unnecessary to press the blade against the face surface in order to recover the face surface. It is only necessary to gently rub the face surface with the blade. Accordingly, the generation of damage on the face surface is prevented, and the amount of the liquid absorbed by the blade is reduced. As a result, the liquid discharging head and the blade can be maintained in an excellent state for a long time.
According to means disclosed in the present invention, it is possible to realize a liquid discharging head and a liquid discharging recording apparatus capable of being used for a long time when the frequency of use of the cleaning blade used in order to recover and improve the quality of printing in a full-color-type recording apparatus or a high-speed recording apparatus is very high, and high reliability is required.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.